The principal research focus is to analyze longitudinal changes in functioning among BLSA subjects. The aims are to characterize intra- individual changes in 14 domains of activity and to study how these changes vary by sociodemographic and medical factors. The data for these analyses are derived from the "Activity Questionnaire II." It has been filled out by BLSA subjects at each visit since 1966. Subjects estimate the amount of time they spend on numerous specific activities, ranging from personal care to leisure. This data set is unique for its time stretch (up to 25 years for some subjects) and its content (the comprehensive scope of activities). Analyses on this data set include examinations of the cross-sectional, longitudinal, and secular patterns by age and gender. Cross-sectional analyses reveal consistent age and gender differences for participation in and time spent doing various activities, especially work, housework, childcare, and various discretionary activities. Comparisons of longitudinal and cross- sectional results show evidence of secular changes in time spent doing work, housework, and childcare by women. Examination of the effect of chronic conditions on time spent in activities revealed that the presence of a chronic condition (diabetes, hearing loss, hypertension, ischemic heart disease, musculoskeletal problems, pulmonary dysfunction, and visual acuity problems) increases the time spent in obligatory activities (personal care, sleep) and decreases time in discretionary activities (socializing, public service). The effect of a chronic condition on committed activities (housework, childcare) interacted with gender so that women increased time in these activities while men decreased their time; this may be a function of gender differences in perception of commitment of activities (e.g., women being more committed to housework).